Timing or drift circuits for loran navigation systems



,Oct- 4, 1952 V R. R. FREAS, JR 2,614,159

TIMING 0R DRIFT CIRCUITS FOR LORAN NAVIGATION SYSTEMS Filed March 11,1949 6 Sheets-Sheet l mgr.

INVENTOR EbeIgJZFPeaQ Oct. 14, 1952 R, FREAS, JR 2,614,159

TIMING OR DRIFT CIRCUITS FOR LORAN NAVIGATION SYSTEMS Filed March 11,1949 6 Sheets-Sheet 5 TITH'ITT" I l I l I 21 57405 i 1& 57/?65 2 4157465 I I l I .L

INVENTOR Zlokrl .Frmzfi". heuz BY i ATTORNEY Oct. 14, 1952 R. R. FREAS,JR 2,614,159

TIMING 0R DRIFT cIRcuITs FOR LORAN NAVIGATION SYSTEMS Filed March 11,1949 6 Sheets-Sheet 4 A Fgia.

yfh fzdr J; ATTORNEY Oct. 14, 1952 R. R. FREAS, JR 2,614,159

TIMING OR DRIFT CIRCUITS FOR LORAN NAVIGATION SYSTEMS Filed March 11,1949 6 Sheets-Sheet 5 1 297 I291 ggfaoaa BY [m ATTORNEY Oct. 14, 1952 R.R. FREAS, JR 2,614,159

TIMING OR DRIFT CIRCUITS FOR LORAN NAVIGATION SYSTEMS XNVENTORlabcgilirm fi:

/ ATTORNEY Patented Oct. 14, 1952 TIMING OR DRIFT CIRCUITS FOR LORANNAVIGATION SYSTEMS Robert R. Freas, Jr., Jermyn, Pa., assignor to RadioCorporation of America, a corporation of Delaware Application Marchll,1949, Serial No. 80,784

My invention relates to radio navigation systerns of the loran typeutilizingithejtime difference in the propagation of radio pulses fromsynchronized ground stations} and to improved left driftrand right driftcircuits for counter systemsjdes igned to produce pulses which haveselectedrepetition rates and whichare delayed selectedamounts. i

The present invention is an improvement on the systemof the typedescribed and claimed in application Serial'No. 33,846, now Patent No.2,523,244, issued September 19,'j1950,'fi1ed June 18, 1948 in the nameor John D.Woodward. Loranisystems require some means for producing whatis referred to as a left drift and/or 'a "right drift of a receivedground stationpulse as it appears on the timingsWeep of the cathode rayindicator tube in the receiver. This will be understood from thedescription hereinafter. In the said Woodward application, it wasassumed that left or right drifts would be obtainedby changing thecrystal'oscillator frequency slightly. In practice, this is not verysatisfactorylargely because the resulting drift is slower than desired,In prior art loran systems it has been the practice to provide specialdrift circuits suitable only to the prior art blocking oscillator typeof timer. These prior art circuits, in general, cannot be applied to theWoodward-type ofcircuit because of the difierencein timers'f I eAccording to the present invention, improved drift circuits are providedthat are particularly,

13 Claims. (Cl; 175381) but not exclusively, applicable toa systemo'fthe Woodward type. Both fast and slow left drift are provided andboth fast and slow right 'drift are'provided.

.The present invention will be described specifically, by way ofexample, with reference to the system described and: claimed inapplication Serial No. 78,482, now Patent 2,551,681, issued May 8; 1951,filed February 26,1949, in the names of Howard C. Lawrence, Jr. andRobert R. Freas, Jr. The said Lawrence and 'Freas system is animprovement on the said Woodward system, the Woodward system requiring ahigher frequency oscillator and counter decade than required by theLawrence and Frees system.

Navigation systems of the loran type employ pairs of synchronized groundtransmitting sta tions that emit radio pulses having a fixed timerelation. Each paid of ground stations preferably transmits pulses at anassignedindividualrepetition rate for the purpose of station selection.The pulses are broadcast so-that they may be received by means ofequipment located in the aircrafts or ships whose positions are to bedetermined. By means of the receiving equipment, the operator on thecraft determines the, time difference between the pulses from the'twotransmitter stations of one pair astheyarrive at the receiver. Since theradio pulses travel from-the ground transmitters to the receiver at aknown propagation rate (i. e., at'the velocity of light), it is knownthat the position of the craft is at some point on a line correspondingto the time difference reading. By obtaining the time difference readingfrom a second pair ofground station's, a second line corresponding tothe sec-1 0nd time difference reading is obtained, and.the intersectpoint of the two lines is the position of the craft. Special maps havingthe, ftime difference or loran lines printedthereon for'the.

several pairs of ground stations are provided for use'withthe navigationsystem.

In order to measure the time differencein the arrival of successivepulses from a pair ofground stations, the receiving equipment isarranged to generate pulses at selected repetitionra'tes; The pulses"maybe adjusted to have a definite time relation to time of arrival ofthe ground station pulses andare provided for the purpose of driving orsynchronizing cathode-ray deflecting circuits. The deflecting circuitsproduce'cathoderay sweep traces on which the received ground stationpulses are displayed. These selected-'- repetition-rate andadjustably-delayed pulses are obtained from a system comprising countersand switching-to be described in detail hereinafter.

For the purpose of selecting a particular pair of ground stations, theoperator selects the particular 'pulse repetition rate for the drivingor synchronizing" pulses corresponding to the rapetition period of thepulses transmitted from said pair whereby the deflecting circuits may besynchronized with the received pulses from the selected pair of groundstations. This repetition rate selection is accomplished by adjustingthe repetition-rate-determining switches of a chain of counters asdescribed in said Woodward application and as described hereinafter.Thus a par: ticular pair of ground stations is selected at the receiverapparatus by setting the said counter switches to preselected positions.This preferably" 9 is done by turning a single station selection knoboperating the several counter switches. Assuming the station selectionswitches are ganged, the station selection knob is turned to apositionindicated on the receiver panel for obtaining sweepsynchronizing pulses having the samerepetition period as that of thepulses being transmitted from the selected pair of ground stations.

Now the received'pulses from the selected pair of ground stations can bemade to appear stationary on the cathode-ray sweep or trace whereasthose received from the other pairs of ground stations will move alongthe same trace.

The pulses, from-= the two transmitter :stations of a selected 'pairxwill be referred to as A and B pulses, respectively, and the 13 pulseis identified inthe present system as the pulse that occursi.

after or follows the mid-pointof the other pulse period. In operation,the A and B pulses are-di-s.

played, respectively, first on two slow-sweep cathode-ray traces andthen on two fast-sweep,

cathode-ray traces, therebynenabling the operator to'obtain analignment'of the A and B pulses by' adjusting another set of switches,.ref.erred to as delay-determining switches, so that the timedifference between the pulses driving or synchro nizing the cathode-raydeflecting circuits equals exactly (the time pu ses. j hsde'sicribed .inthe above-mentioned Lawrence andlFreas, application, certain .of saiddelay-- determining switches are switches connected to aid ,chain ,ofcounters Just, as described in .said Woodwardapplication, for example,but at .least one .of the delay-determining switches ,is .con-

iiference between .A and B nected tona tapped delay line :orthe likeinstead.

It; will benoted that the chain of counters has two sets, ,of switches,co'nnected'to-it, one for determin'ing the ,repetition .rate and theother .for determininginpart the amount .a pulse is dehas no reset pulseapplied to it.

transmitters, and this time difference can be read The IfiISt stage :ofthe ffdivide 4;:unit is a binaryscounter (*a-zmultivibtator) :tha'ztisthe last stage, strictly speaking, of the counter chain.

The second multivibrator of the divide by 4 unit .cnunters arepreferably of the general type described in application Serial No.580,446, now Patent 2,521,188,, issued September 12, 1950, filed J5Mai-chi, 1945,.3in-the name of Igor. E. ,GrosdofiL W Morespecificallmxth'e counter and counter switch- .ing combination utilizesprinciples described'in application Serial No. 719,035, filed December28,

layed. .The, action of each is independent of the action'oftheother. v

The reasonfor employing a delay line'with .delay-determining switching.connected thereto is that it; simplifies theequipmentand, .what is .moreimportant, its use makes it ,possible to begin the counter .chain. with1a lower frequency gdecade counter unit and thus .avoid serious,difliculties encountered in; operating such .a .unit :at a very highfrequency.

',.The adjustment for the display .and alignment of;the Aand .B pulsesis accomplished .by first setting .the A pulse .at .the .left end .ofthe upper slow-sweep trace ,(by means of drift switching circuits.described hereinafter), when the :receiving apparatus .is switched to.an operating position marked No. .1. The B pulse will .then appear .onthe lower cathode-ray trace and a variable .indexmarker may .now belocated'under the B pulse, .this being done by adjusting the severaldelay switches to delay the variableindexrmarlier the correct amount.The apparatus is then switched to .a No. 2 fast-sweep operation positionsothat the A and .B pulses appear on :two fastsweep traces,respectively. The starting time .of the fast-sweep :trace on which the.3 ,pulse "appears always coincides with the start of said variableindex marker as determined by the delay switches, while the startingtime of the fastsweep trace on which the A pulse appears, coincides-withthestart of the slow-sweep. trace. Therefore, by a more exactadjustment-of the delay switches, the adjustable fast-sweep wave iscaused ,to start at the proper time to bring .the A IandjB pulse intoalignment. Inorder toginsuregexactalignment, theA and .B pulses shouldbe made to .have the .same amplitude, .andjan amplitude balance controlcircuit is provided "for this purpose. .A-fterthese adjustments havebeenmadathe time difference between the starts of thefastsweep willexactly equalthe time dif ference..between the .A and YB- ;pulses fromthe 19A6,in,thename of Charles J. Young, now Patent No. 2,490,500 issuedDecember 6, 1949, but,-as set .forthin saidWoodward-application,.includesiim- 1 provements .;over and additions ,tothe zcombinationedisclosed byYoung. r The delay pulses .having a .delaythatlisrdeter: mined by the settingsof :the delay-determining switchesare: applied to .a delay .line and aretaken off taps on the delay line.through .a -,delay-deter mining switch for obtainingdelaysin-stepsof-rone microsecond w I An {object .of the presentinvention is to ,provide an improved method of'andimean for determiningthe time diiferencebetween electrical pulses. g .A further ,object ;ofthe ,invention is ,to prouide' improved receiving equipment for a radio.nayigation system of the ype utilizing the propagation of .radio:pulsesfrom pairscf synchronized ground stations.

taining adirect reading of thetime-diiference between .radi'o pulsestransmitted from synchronized ground stations; .A. stillvfurther-"object of the .inventionli 113011310,- vide .an improvedmethod of and means forebtaining left drift and/or. right -.;drift ofthe received pulses appearing ;on an indicator tube .:of receivingequipment for :a radio navigation .system pf the type utilizing thepropagationlofzradic pulses from pairspf synchronized ggroundsstations.

The invention will be better understood :from the following descriptiontaken in connection with the accompanying drawings 'inwhich:

Figure 1 .isa block and circuit diagram ofnavig-ation receiving apparatudesigned in :accordance with one embodiment of theiinvention, Figure 2is .acircuit diagram of the left drift and right driftswitchingcircuits,

Figures '3 and 3A, .to be placedside by'side, are blockandcircuitdiagramsof thecount'er and the to in explaining "the operation{of the navigation systemshownin Figure .1, 1

figure 56.; is a group of graphs whicharereferred The decade to inexplaining the operation of the counter system shown'in Figures 1,2 and3. r

Figure 7 is a view of the slow-sweep cathoderayhtraces appearing onthescreen end of the cathode-ray indicator tube that is included in the'apparatus of Figure 1 and of the received pulses A and B as they appearon the'traces when they are aligned,

Figure 8 is a view of the fast-sweep cathoderay traces on thecathode-ray tube indicator and of the received pulses A and B as theyappear on the two fast- -sweep traces, respectively, during the nextstep in Obtaining more exact alignment of the'A and B pulses,

' :Figure9 is a view showing the fast-sweep traces of I Figure 8superimposed or collapsed for the final alignment step and showing the Aand B pulses exactly aligned and superimposed,

Figures 10 and 11 are circuit diagrams of the horizontal deflectingslowsweepand fast-sweep circuits, respectively, employed in the systemof Figure 1, and p Figure 12 is a circuit diagram of the delay lineshownin block in Figure 3A.

"In the several figures, similar parts areindicated by similar referencecharacters.

Tr s COUNTER CHAIN AND ASSOCIATED REPETITIUN RATESWITCHES AND DELAYSWITCHES Referringto the navigation receiving appara- I delaywhereby itmay be shifted along the sweep trace when 'a slow sweep is used andwhereby it may be utilized to trigger the adjustable fastsweep when thefast-sweep is used.

The amount the variable index marker pulse 7 is delayed is determined bythe setting of time tus shown in Figures 1, 2, 3 and 3A, thepulseproducing system comprises a crystal oscillator l0 that produces asine wave voltage of stable frequency which in the example illustratedis 100 kilocycles per second, the repetitionperiod being 10microseconds. The frequency of the crystal oscillator output may beincreased or decreased slightly by a manual adjustment as indicated atthe control knob H for obtaining a right or left drift of a receivedpulse on a cathodeeray sweep trace but it is preferred to obtain rightor left drift by means of drift. switching circuits (see Figures} and3), which embodyithepresent invention. This prevents the. possibility ofinterrupting the continuity of the oscillator output, a disadvantage towhich the prior art circuitsare known to be susceptible. Suchinterruption changes the location of the received pulse on theindicator, which isvery annoying operationally.

The crystal oscillator I0 supplies signal through a left drift switchcircuit LDS' (shown in detail in Figure 2) to drive a decade counter I3for producing periodic pulses which recur at the rate of 10 kilocyclesper second. The repetition period or,,time, interval between successivepulses is, therefore, 100 microseconds.

The frequencyof the 100,15. pulses is divided by 10 by' means of asecond decade counter 14 to produce 1000 s. pulses. Thefrequency of the1000 [15. pulses is divided by 10 bymeans of a third decade counter llito produce; 10,000 s. pulses, and the frequency of these is divided by 4by'means of a frequency divider or a counter 11 toproduce 40,000 s.pulses. As explained hereinafter, the decades and the first stage of thedivider ll comprise a counter chain. The output of divider H is in theform of a square delay switches ID, SZD, 83D, S4D, and $51). With theexception of switch ID, these switches, as shown in Figure 3A, aremultipole multicontact; switches that are connected to the .severalanodes of the multivibrator tubes in the counters. The switch ID isconnected to taps on the delay line DL for obtaining a delay in onemicrosecond units as explained hereinafter.

The repetition rateof the pulse from gate No. 2,-as well as that of theother pulses takenoff the counter chain, including the pulse taken off agate circuit No. 1, may be varied for the purpose of station selectionby means of repetition rate switches SZR, 83R, S4R, and 85R, which aresimilar to the delay switches SZD, etc. andwhich are connected to theanodes of the counter tubes in .a similar fashion. Pulses taken off theswitches S2R, etc. are passed through the gate circuit No. 1 and aresupplied to a reset pulse generator 49 which may comprise a Thyratron asexplained hereinafter. i

The output pulses of the pulse generator 49 have the same repetitionrate as the output pulses from gate circuit No. 1 but have agreaterenergy content. Positive and negative polarity pulses are taken of]? thepulse generator 49 by way of leads 42 and 42A, respectively. Thepositive pulses are utilized both to drive the slow sweep circuit, asdescribed hereinafter, and to reset the counters. i

As will be explained in detail hereinafter the positive reset pulses forthe first counter stages of decades l3 and I l are applied to saidstages by way of a right drift switching circuitRDS shown in detail inFigure 2. i

Thenegative pulse from the pulse generator 49 is applied to the leftdrift switching circuit LDS. The left and right drift circuit operationswillbe described hereinafter with reference to Figure ,2. v

A detailed description of Figures 2, 3, and 3A will be given later, butfirst the other parts of wave having the repetition period of 40,000 s.

This square wave is always symmetrical regard less of the repetitionrate since the reset pulses are not applied to the second and laststages oi,

the divider l! as will be'understood from the later detaileddescription. The square output wave is passed through a cathode followertube.

[8 and from it are obtained a vertical separation the navigation systemwill be explained.

In the example being described, it will be assumed that the first pairof ground stations transmit the A pulses With a repetition period of40,000 s.

and transmit the B pulses with a like repetition period; that the secondpair of ground stations transmit A and B-pulses having a repetitionperiod of 39,900 s; that the third pair transmits 39,800 s. pulses; thatthe fourth pair transmits 39,700 ,us. pulses, etc. It is apparentthatfor station selection at the receiving apparatus,

the operator must be able to select corresponding repetition periods forthe output pulses'of the counter system which control the cathode- ,raydeflection cycle; namely, periods 'of 40,000

304000 s 29,900n s setc; maybe employed. Or, eel-anotherexamplatrepetitionperiods of 50,000

I ILSQ, 49,900 s etcrmay be employed- GA'rrIomr RAY, T monPRESENTATIGNIV cathode-ray tube presentation. e

, r "In Figure '5, theigr'aphs X and Ws'how the wave shapes of the.slow-sweepand fast-sweep horizontalflefiectingwaves,'-respectively, forobtaining the desired cathode-ray traces. The wave V comisadjustable intime and determines the starting time 't' of the wa-ve f g of the graphW. The

starting time t of the "variable index marker in relation to the fixedindex marker maybe adjusted by'adjusting the switches 1-D, 'SZD, etc.(Figures 1 and 3A), aswi-ll be explainedherein- ,after,'--for aligningthe 'A'and B pulses. By means o'fgarigedfunction switches,three-switching positions identified as positions No. 1, No. 2, and No.filare used successively fin aligning the A and B pulses. "I-t 'will beunderstoodthat while'the pu-1'ses7A- and B and'their correspondingiastsweep traces appear alternately on the cathoderay tube screen, theyappear to "the eye to occur simultaneously because of persistence ofvision, lag of phosphorescence ofthescreenor both. .As shown in Figure5, the '3 pulse is theone that occurs'after the mid-pointer the A pulseperiod, and "consequently the "time interval, whichxe'lapses between theoccurrence of a B pulse and the succeeding A pulse will beless thanone-half pulse interval. I in- Eig-ure 5, the start of -one'iast-sweep(hi) coincides with the start-of aslow trace, while thes'tart of theother fast-sweepKj g) coincides with the variable index marker. v

By employing the left-rightdrift switches. a momentary change in therecurrence ratemay be produced 'tochange the location of the pulses on'thetrace by drifting them along the trace.

Specifically, it is possible for the operator to locate'the A pulse atthe left side o'f'jthe upper newer-ace, which in turnwill cause the Bpulse to fallon "the lower trace, and the variable index marker may bemade to coincide With'the B-pulse. Therefore, when thefunction switchesare turned to position No. 2, the A pulse will occur during thetrace-described by the fixed fast-sweep oleflectingwave while the'Bpulse will occur cluri'n'gthe trace described by the variable fast- Affiner adjustment will permit the operator to align the A' and B pulsesso that the time elapsed between the start of the respective fast sweepsand the corresponding pulses are equal and occurs during the expandedparts of the traces, "thereby providing good accuracy fordeterminingjthe time delay.

In'the present present system, after the A and CB pulses have beenaligned with the receiver switched successively to operating positionsNo. -1 ,i-No."2, and'No'. 3, the desired time diflerence m'timerinterval is read 011 the delay switches 1D, 82D, .S3D, SAD, and 85D(Figures '1 and 3) which indicate; respectively, microseconds in 'units,tens, .hundreds;thousands and multiples of sten thousand. The timeinterval thus obtained iisy-the amount that the, starting "time t of:the =variable-..index marker has :beenadelaye'd in time As will beseen;

- with-respect ate the mid-period d (Eigluzlteffif) :01 the deflectinwave-cycle in ordervtovalignithe I AJandaB pulses. r I I maybe-noted:that the upper :fastitracc h.i 3(illustratedvin Figure .8)"riszproducedjby ingi 'wave- W; "The lower fast trace f,g irtigure 8) isproduced by the second iast-sweepwayg prises apair'of recurring pulses,the second of which (referred to-as the variable index marker) GENEnxLDEsoRI PrmN or Cxr onn RAY PRODUCING CmouITsf Referring to Figure 1 andto thegraphs ure 5,.the output of the pulse eneratorjhis supplied ,overaconductor Gla to a slow-sweep deflecting circuit I I5 for-producing asawtooth voltage waveX. I H

The output of the divider r l-1 is :a xl ectangular I voltage wavewhichappears runchanged atrthe output of a cathode-follower tube. [8 a-Suing waveC'. a v To produce the fast-sweep Wave git-i -(H311!!-fleeting wave W (Figure 5-), the wave 0 is supplied over a conductor 198 toladifienritiating circuit I05 to produce apulse |;-05 A. 'I'hepulse [05A is also utilized ,asthe fixed index marker of the wave V'.

The circuit for producing the variable index marker of wave V comprisesthe counter chain, c

the delay line DL and the associated ,del-ay switchin the said markerbeing obtainedirom the adjus'tably delayed pulse IJ. taken from thedelay line DL byway .of the switch 11).. v,The delay line ,DL hasdelayed pulses supplied .t o it from the gate No...2 ,as described,herein fi i, the delay line providin the final precise delay in stepsof one microsecond units. It is the wave U that controls the timing of,the adjustable fast-sweep portion f-g of wave W. The delayed fpulse'U isductor H9 to the mixer 10.5.1

pear .as, the wave .V which drives. the fast sweepdefiectiri'grcircuitfllfl to produce the wave When Ithesystemgis in the.No. lfoperating pp? sition, .the fixedand adjustable index markerpulsesflof (the wave V are applied to the vertical deflecting plate 368of the indicator tube" .139

through .a ,lead .38 switch 350., ,ares'istor and to mix the remainingclipped positive pulses T with the pulses U- .Thus, the Wave 1Visobtained atlthe output of the clipper-mixericom-x bination. The mixerwhich mayconsist of" two vacuum tubes .having 'a common anode ire sistoras s'hown in Figurell, reversesfthe polarity of the pulses. the .mixerI06 .are .of, equalamplitude due Ito. opf-feration-of the tubes aconditionwhereg'ridpnd plate voltage approach equal amplitude. The Widthof the applied pulses U and :l054;is ;s hort compared to that of theplate pulses, the width of the latter being controlled .by a capacitor:-resistor combination in the "plate-circuit and therefore beingindependent .of 'the width er the incoming wave. This-,capa-citor-=r,esistor ,combination comprises. a capacitor Cl andthejplate resistor,R;l.

. The-wave V is supplied :to the ,fa'stesweep :de-' ,flecting-icircuit422 :shown :in detail inflgure jl'l supplied over-a my The mixed wavesUand 105A pass through aclippe'rfll2l ,andlapf The wavesin the plateLcircni of and described hereinafter. The narrow negative pulses of waveV produce the fast-sweep wave W having the useful deflecting portionsh-.-i and f-g. The deflecting waves W and. X are .ap-w

plied fromthe circuits I22 and ,Iliithrougha wave-selecting swi-tch I23and through arhorizontal deflecting amplifier I24 to thehorizontal;

of less slope across resistor 3132. flhese twogyolt 1 ages ofdifierentslopes appear at-theftap 3 33as the? sumof the two voltageswiththe ,Voltagefqir the steeper, slope slightly delayedbythe delay.

networkjsectionfllc." The wave form of the wave w -follojwi said slightdelay-is approximately;logarithmic: It should be understoodthat,the-fast sweep wave W neednot-ibe of, the wave: forml describedand, in fact, maybe linear. :1;

The above-described fast-sweep cuit is described and claimed inapplication Serial "The switch I23, whichtis: one ofthe function Nswitches, has three contact points and three corresponding .switchpositions, referredto as operating positions, which are identified, reading clockwise, aspositions No. 1, No. 2, and No. 3.

There are several other operation position or function switches,described hereinaftergthat likewise havethese three switch positions andwhich are gangedwith the switch I23.-

Switch'I23, when in operation position No. 1, functions to apply theslow-sweep-wave X to the horizontal deflecting plates I38 and, when inoperation positions No. 2 and No. 3, functions to-apply the fast-sweepwave W to the deflecting plates I38.

The fast-sweep-deflccting circuit I22 that is driven by the wave V(comprising the fixed and variable marker pulses) to produce the fastsweep wave W will now bedescribed with reference to Figure 11.

The jest-sweep circuit Referring more specifically to the circuit I22for producing the fast-sweep wave W as shown in Figure 11, the circuitcomprises a vacuumtube 316 and apulse-shapingnetw'o'rk that comprisestwo sections consisting of cathode resistors 33I and 332 s huntedbycapacitors 33 3 and 334,"re-

spectively, identified as network sections 3 I Ia and 3IIb. The shapingnetwork further comprises a delay line section 3IIccomprisingseriesresis tors 336 and shunt capacitors 331 connected acrossthe cathode resistor 33! and terminated in a resistor 338 and in thecathode resistor 332, The fast-sweep wave W is taken off the resistor338 through anadjustable tap 339, the setting of which determines theamplitude of the wave In operation, the capacitors of the network sec-jtions 3IIa and 3IIb are, charged through the No. 583,255, Inow' PatentNo. 2,463,969, issued March 8, 1949,.filed March 1'7, 1945 in the nameof George D. .Hulst, Jr. and entitledrCathode Ray As previously noted,the startingtiine tot the I -sw p ave f-c is determined'fby justment ofthe pulse U (and in turn'bynthe variable index marker of wave V)awhereby the start of the wave f' g may bemade to precede the received Bpulse by the same amount that the start of thewave h-e-i precedesthereceived'A' pulse, this being the condition .of alignment of, the Aand B pulses. It should also be noted that the wave 'f-g isidenticalwith'zthe wave IL -4i whereby exact alignment of the A and B pulses onthe cathode-ray traces is obtained (as shownin Figure 9) when theabove-describedltiming relation exists. a o i An improved fast-sweepcircuit described and claimed, in copending application Serial No.674,184, now Patent No. 2,449,169, issued Sep: tember 14, 1948,filed'June 4, 1946 in the names of Paul F. J. Holst and LorenRrKi'rkwo'o'd and entitled Defiecting Circuits, may be employedi'fdesired. 1 Y i r The slow-sweep circuit Referring more specificallytothe slow-sweep deflecting circuit 'II5, ,as shown in Figure 10, itcomprises a vacuum tube 318 andfanetworkiri the cathode circuit thatcomprises acathode resistor 342 that has an adjustable tap3'44tliere fon and which is shunted by a capacitor 345; Positive bias is applied tothe cathode of the tube 3I8 by connecting the lower end of cathoderesistor .342 to the junction point "of apair.of

, bleeder resistors 3I9 and 320. This l'pjreventsithe 32I, the'capacitor 343 is charged suddenly from anode resistor 34I' and the tube3I6 to a certain voltage level between successive pulses of the wave Vto bring thetap 339 to the voltage (21 (Figure 5). Upon the occurrenceof each negative pulse of the wave V, the tube 3I3 is driven to cut-offand the capacitors 333 and 334 discharge through the resistors 33I and332, respjecf tively. The section 3IIa comprising capacitor 333 andresistor 33I has a fast time constant tube 3I8 from drawing current atthe end of the sawtooth cycle so that flattening bf the saw; tooth waveis' avoided The o eration s'asjrolg lows: Each time one o'ftherlrbsitii/ el 20,0(J 0" Ls.

pulses from the lead Gla is supplied, to the'grid of the tube 3I8 by wayof a couplingQcapac'itor the anode voltage supply through the tubei'f3I3to a certain voltage levelto bringv thetap/M l to the voltage level e2(Figured), 'Atfthe, ehd ljo f each positive pulse, the capacitor, 343discharges slowly through the resistors 3,42 and ,3I9.thusi producingsuccessively the slow-sweep sawtooth wave portion cbb and the sawtoothwaveporf tion 0-12 at the tap 344. Y

In Figures 10 and 11', the values or certain cit:

cuit elements have been indicated, merely by whereby the'discharge ofcapacitor333 produces a voltage of steep slope across'resistor} 33l. Thesection .3IIaficomprising capacitor 334 andresistor 3 32 has a slowertime constantwher'eby thejdischargeof capacitor 334 produces a voltageway of example, in ohms,.megohms, microfarads and micro-microiarads. 1 5

THEJReiDI O-RECEIVER v I T A 3 v sf m par stations (Figure 4) arereceived 'a a ceiver of thesuperhetcrqdyne type, compri radio frequencyamplifier indicated The-nandnp'pulses are su (polarity over a conductor3'66,-a"conductor 381' 'fingt-shownh p 1 "In "operation," during theperiods that the 1 a men on detector and video frequency amplifier 364iand ycapacitcr 382 to the ul i fvertical" cleplitiideonrthei cathodera'y tube screen by employing a differential control circuit de-i scribehereinafter.

era-ted; as; illustrated in Figure 7- while the re-a ceiver is onthe No.1 operation. position by ine'ans either rectangular. Wave CfiFigur'e 5)supplied, f-ifomthe cathode'fo-llower tube l8- (Figure: 1):;o'veii,

acond uctor" 369 to-the No; 1' contact pointoff-a traceseparationswitch31l, and ovei'a: eond'uc tor-312',to"; the upper defiectihgplate3681 of the cathode ay tube I39; l Thus, the portionof the wave-oi whichis positive as itappears on. the upperplatei388, holds;.the cathode-raydeflec tie up a certain" amount during, the occurrence oflthe:slow-sweep deflecting .wave c-d.

- v @Bmd as illnstralted in Figure 8 during the No. I 'zvoperationposition also by means or the rectangular wave C,

rovicied so; that only the traces f+ -g- ;and hi appear onthecathode-ray screen t 'BRII-LEIANCE CON-Thor, diode 324 is rovided tocontrol thebril fiancer thetrgacesjcn the cathode ray tube so enhyfpreventing changes in bias on the oath o tutegna'sn due to theapplication'of gfpulses. aleak resistor 328 is conne'cted oss-tl iediode 3'24 and the cathode of the diode 324 isconnected to a variablebias voltage source tisnk g wave are positi e at ageanode of the 4, theinipejd'ande' of the diode 32 f isver'y a; Thus, regardless of the i 1of; its cathode f t b1a g ave and regar i s qf tzlietherany blank ngwave is being applied, the

duri g the cathode-ray swe ten substantially the voltage on the cathodeof the; diode 324v. newsman GAI CONTROL Cmcrirr "A differential gaincontrol circuitjor the amplifier 36! ofthe radio receivenpreferablyisprovided, as shown in Figure 1, for the purpose of keeping theamplitudesof the A and B pulses a substantially iat the' receiveroutput; thus fanitatingutiie A and, B Y pu1se' alignment." T gain 66fol-circuit includes a resistor 343 c011 fiectd' he eenft-heanods of'the *two' tubes of the lasemumvibiatoiin the. final divider 11 N25fitter-swi trai s s mi-news '4 :The'sl'ow weeptracesan'doc'd are sep--asthma a p 12 (Figures i-and- 2). gain-balance tap'on resistor 343may bemoved 6':

"either side of the center thereof to decrease the gain of the Ri-F.mnplifier 3E duri'n'g eitherthe: reception of the pulse A or the pulseB. "IIhe vow;

agexa'tth'e gain balance tap: is: suppliede-throug it a 1ead'340, acapacitor M L-anda resis'toir;346- to the zanodeof a diode 3415. nd.to.,the ,No.= i and-No.. 3. contact points-oft idifferential gain:control switch- 348; 'IThus, When thereceiver is on either the No;'.2;or .No. 3}.op'eration position for pulse alignmenton the 'fast sweeps,the-differential gain control voltage.- i's applied through i theswiteh1348 and a conductor349 to: the gains, i control grid of. an amplifiertube in the Ri gi i amplifieii '3161. ,1 The. differential gaincontrolroperation with the receiver oneither No. 2 cr.No,-;-3opratiunposi? 1 low so thatits anode is practically at thebias po-'again to lock them tion is as follows:

i 3 When the gain balancetapfis' atthe center of resistor 343, novoltage wave is appliedatothe diode 341. When the :tap isxonone sideofthis center orvbalance position, a wave of one. polarity is-appliedtoithe'diode 341; I

the 'other side of'thebalancepoint, a wave of the-opposite: polarity isapplied touthefdiode 341 The .diode 34T-functions to'supply avnegativebias during the negativehalf-cycle followingv a posi tive cycle' of anapplied wave.:1For example a positive half-cycle causes diode current;to.charge capacitor 344, and during the following negative half-cycle"the capacitor 344 discharges slowly througha resistor 35 I. connectedacross the. diode 34-Igthus making the anode of diode; 34-? negativewith respect to ground and reducingthe gain" of the R.-F. amplifier 36!while the B pulse v(or the A pulse) is bein amplified. a iWithiswitch348 on the N0 '1 operation posi' tion for p ulse. alignment,normal operating bias voltage. 'V is onthe R.F.- amplifier 36! i jDETAILED DESCRIPTION OF COUNTER CHAIN AND SWITCHING or FIlcUREs3 AND 3Amore detailed. description will now be given; describing the system ofcounters, switches andv gates for obtainin Pulses of/ the desiredre'peth tion rate and of the desired delay. The specific system shown inFigures 3 and 3A providesheighi: different; repetition rates of 40,000s; 39,900.;Ls; 39,800 s, etc. for selecting any one of eight pairsofstations according to the settings of switches SLR, S3R, etc. As tothe pulse delay, this par: ticular system delays a pulse from 0 15. toover 19,( )00@ 4s according to the settings of switches lnszD,s3D,.etc;- v v Referring to Figures Bland 3A, the,cha'in: of counters,the repetitionrateswitching, the delay switching, and the gating orcoincidence'circuits are shown in detail, by way of example. The firstdecade counter, which'is identified as counter Noa 21t'o facilitatecomparison with-the above-mennoses Woodward application, consists f,multivibrat'or -likev locking stages om'prising amine triodes VI, V2, V3and1V4. I'Ihese stages each have two positions ct restat one or theotherof which they stay locked, when tripped thereto; untilsome appliedvoltage c;- currenttrips them V I s v in the; other position6 In; theembodiment shown, application of negative vol-t age tb fthe anodesfandthence to the grids of the locking circuit tubes willreduc'e current inthat time drawing urrent; and start the tripping a tion which switchesthecurrent thrcnigh the other lar'and to simplify the diagram have beenillus- Anfladj'ustahle diiierential when theptapi is on are referredcounter-No. isillustrated in detail: andlcomprisesonly twomultivibratorsMl and M2 since it divides by 4. The multivibrators inthiscounter are similar to those employed in .the decade;

counters. However, the first stage MI is the final stage of the counterchain. These'cond stage M2 has no. reset pulse appliedto :it and it does'not supply any pulse to the: coincidence tube of the repetition ratesystem as .will

be apparent from the followingdescription.

The repetition rate switching Associatedwith each decadecounte r is athree pole, ten-position switch (Figure 3) for determining the pulserepetition rate. These switches.

to as em, em, and sm. While ten switch positions are shown forclearnessof explanation, not all of them are useful in selectingtheeight stations in the example described.

There is also a single-pole two point switch S5R for the binary counterMI.

The switches 82R, 33R, 54R, andSBR and the contacts thereof are coupledto the anodesofthe locking circuit tubes whereat the potentials rise andfalldepending on which tube of. thepair .is drawing current. Forexample, the anode VIA of the left-hand or A section of the tube VI isconnected. to alternate contacts of pole PI,- of the three-pole switchSZR. The anode VIB of the right-hand or B section of tube VI is con,-nected to the remaining contacts of this pole. The anodes V2A, VZB,andV3B of tubes V2 and V3. are connected to staggered pairs of contactsof; the second pole P2, etc. The basic details of eachdecade and howitoperates is covered fullyv Grosdoif application Serial No. 580,446,referred to above and consequently, no: detailed explanation will begiven here. Associated with the binary MI of counter No. 5 is thesingle-pole two-position switch S5R that functions with switches 82R,SBR, etc. for determining the repetition rate. Although not soillustrated, the switches'S2R, 83R, etc. preferably areganged so asv tobe operated by a single station selection knob. I

produced after the predetermined count has been reached is obtained bycombining the proper volt ages from the anodes of certain tubes in allfour counters. For example, to select stationLl the repetition period ofthe last multivibrator M2 of counter No. 5 is made 39,900 microseconds.

The basic purpose of the counter circuit is to Since the first stage MIof counter No. 5 is the final one in the counter chain to be reset, asexplained hereinafter, the desired result is obtained by making therepetition period of its output wave D (Figure 5) one-half the saidperiod of; 39,900, Therefore the switch SZR ou as or 19,950 as. counterNo. 2 is set on position 5 which is the tens count, switch 53R oncounter No. 3 is set on position 9 which is the hundreds count,.switch54R on counter No. 4 is seton position 9 which is the thousands count,and switch SSR on counter No. 5 is set on position 1- which is the tenthousands count.

. The voltage pulsescollected by the switches are combined by means offour .vacuum triodes 21, 28,

ing the: switches to ground. Each triode is biased by means of a voltagedrop across a. by-passed cathode resistor. This combination of pulses isobtained by the connections of said switchesto the control grids ofthese fourtubes. The 'anodes of the tubes are connected together to produce a single pulse, which represents the sum of the collected pulses,and feeds the same by way of resistors 31, 38, 39 and 4| and commonresistor 42a to the grid 33 of a final combining or coincidence tube 34.The tube 34 is connected in an amplifier stage with its grid grounded bya resistor 45 and its cathodegrounded by a resistor 46 and its anodeconnected to the plus terminal of a direct currentsource. The anode ofamplifier tube '34 is coupled by'a capacitor 4''! to the control grid 48of an output or reset pulse generator tube 49, the-purpose of which isto deliver the combined or output pulse of positive polarity to all ofthe tubes in all of the decade counters and to the tubes in the binarycounter MI' to trip the same back to their starting position forsuccessive operation of the counter chair'r'and also to deliver a pulseof the desired repetition rate to the slow sweep generator by way of thelead 6m. A negative bias voltage is applied to the grid 48 of tube 49through a resistor 45a. Also, as previously mentioned, the reset pulsesare utilized for right drift and negative pulses from tube 49 areutilized for left drift.

Referring to decade counter No. 2 which has its switch 32R. set atposition 5, it is noted that for each position of the switch, adifferent combination of voltages from the eight tubes of the counterare used as explained in the Grosdoff application Serial No. 580,446.The voltage on the switch SZR, as applied to the grid of tube 21 reachesa certain maximum positive value only when thecount is at the value forwhich the switch position is set and'the final desired output pulseapplied to the gridoftube .34 is obtained only when the propercombination of voltages occurs simultaneously on the selected tubes ofall four counters. For-example, in decade counter No. 2 .onthe count of'5,-the voltages selected by switch S2R are those at the anodes of tubesVIBand V3B" and V4A. This combination of three voltages raises thecontrol grid of tube 2! above its cut-off point so thatconduction is initiated initub 21 and the potential on its anode and' at' resistor 3Tfalls. The procedure for selecting voltages bytheswitches willbe'understood by referring to the graphs of Figure 6.

:The several graphs of Figure 6 show the-voltages appearing at theseveral anodes of the tubes VI, V2, etc. The graph identified as VIAshows the voltage on the anode of the left-hand or A sectionof' tubeVIA, for example. The disym metrical characteristic of the graphs forthe tubes V2 and V3 results from the feedback em- 1 ployed'to obtain adecadecount as explained in Grosdoff application Serial'No; 580,446. Thedots indicate the plates that are selected to obtain a given count. Forexample, the anodes VIA, V2A,

and V4A are connected to switch points 0 to ob- 28, 29 and 30 when theproper voltages are ob- I tained by the settings on switches 83R, S4R,and SSH. When the final pulse whichrepresents the final combinationofvoltages from thetubes 21,

28,29, and .30 isireached, the voltage applied to the-control grid ortube 34 is reduced (negative) torsuch; at. point: that conduction inthe: tube 3.4;

ductiveg thispoint: being. when the.- counterr chain" hasireached. thepredetermined. count;- for: which; it:;iS:ad;i'11S.ted..

l. At. the: instant when: the counterchain pro-- ducesits outputpulseatz the. plate; of. tube 34-, ,this:

011th .ulseis appliedtothepulse:generatorr ube: 4-9; whichrpreferablyis; a: vapor tube such. as a. Thyraztron sc'thataiarge;current output: is ob;-

. tainedat the; output, terminal 5| of.the:load*ir.e;;-

sistorlfia- Preferablm, the tube 49 discharges: a;v capacitor: 49aWhich: receives a chargewfronr the; 13+ source through a: resistor 496..,Thus a highjenergy outputpulse. is produced. From ter;- minalp 5| thepulse: is; applied by way; of? condenser. 52'; and lead42 to reset. the:counters. of; thecqunter chain back tothe zero-or startingposition; Thisresetting'functionis, accomplished by application of the output pulsewhichis positive; in. polarity, to.- the grid; circuits. of: all the;

tubes in. the. counters. which; drawcurrent: in. the.

starting; position. As previouslystated; the; reset pulse is not appliedto; the;multivibrator-M2; of theyfrequency divider-I1 I Thereason fornotapplying: a reset pulseLto the;

'multivibrator M2 is thatit must. supplyasymxtubes: 2-7; 28;. 29 and, 30are: simultaneously con 11m suppliedito vacuum tubes. .51,,58?;.5e,;andwhich;

compriseith'e. gate circuitNorZ ('Fi'gureal x Theses tubes and their:associatedi circuits: correspondilto; the; tubes' 21,. 2 8,.29,.ahd'310; and. their: assnci-aited' v circuits previously."described;

The:coinciden'ce tube 612 .(toiwhichthez'outputsj ofi tubes. EiTtOSmarts applied). and the Thyratmm tube 62 correspondito: the-.tubeszB-l.andfj 49;. spectively; of: the:- repetition rate switching" one. cuit.Delayed pulsesapptear; onithelea'dalz 95.1. The lsetting'jofi switchismdetermines".- thezdelaw in tens, and the settings of switches 53D, 84D.and SSD determine the; delay:- in? hundreds. thousands, and. tens, ofvthousands, respectively.

15; For examplei if" the delawswitches" 82-131; 83D,

metrical square waveiiwave C.in-.,Figur;e;5-)1 just? as-vin; the. caseof the -Eccles-Jordan oscillator. showm in. Minneman: application:Serial No; 744,239.; Furthermore, there-is no: necessity. for; apply; arreset: pulse tothis; last multivibrator" for: changing the 1' repetitionperiod. This: will; be understoodtfrom-the following,

- If: the desired repetition period of the. wave. C

(Figure. 5) from the: last multivibratorpMt" is. to;

be 39,900 it. is. only necessary; to; make the. repetition period of:the-.wave D (Figure. 51,,from: the. preceding multivibrator. M l19,950,- as. since; the last. multivibratordivides bya- 21. This. of;course. is accomplished byitheresetting; action described. Similarly,for." anyother. repetition the. desired repetition period. for "the;outputgwave: D ofthe ;first multivibratorMl' of'counterzNo; 5,; whichrepetition period isi-one-half. that ofrthe;

output. wave CL. For. the particular; example asRErETITIQN'RAraswrromNce 5O period, thesWitchesS-ZR,S3R,,.etc':arerseti'toygive.

S4-D,'-;and- S5D aremfpo'sitibns 5; 75.65 and*"0;-,re' spectiyel'yg. asillustratedi when pulse alignment onthe ca-thode-ray tube screenisobtainedi; their the: reading from these switches is- 67-50 microeseconds; there. being mo -microsecondunitreadi'ng: so; that" thel'ast=figure is zero; For convenience; in settingthe delayswitches=S2D; S313;etci, their ganged, switch arms. preferably." are operated by rotatable"knobs 2-D; 313, etc: which" carry pointers that indicate" the delayset't-inggs j v To determine the" delay in one microsecond units the"pulses from the tube 6-2 (delayed to? withiir't'en microseconds=ofthedesire'd'delayif are applied by way of lead M9? to thedelaylinerDL'which. provides a; delay of one microsecond: section: The line DLmayheroftheconventibnaf 1r section. type: suitably terminated iir. aresistor" TR to: make it" non.-,reffectiiig:

catemicrosecond: units. j The 'final delayed v is takencfi the" switch;arm of switch tD b lead lilflfi'. v It", will" heapparent? that: with.the switches IDjj to 5D on positions-8;, 5, 7;, 6, and; 0'"as:i'llustrated;. the: pulse. appearing-on lead. MBA is delayed 6758i microseconds;t he; unit reading-beingobtainetliby means: of delay: line". 1313.. IThis reading-of '6758 microseconds locates one: of. the. navigation orloran lines of position. on the map" prepared. forruse' with theequipment;

Instead of tapping; a' delay-line: or network';;.a-=. picks-up electrodemay be' associated? with tl'rfef. delay? line so; that; it. hascapacity: to: difierent'i poiht's'in'the networkiastheelectrodeii'smovedi 'Il represent invention is; not. limi'ted'tmth'e useof v a1 particular kind offl' delay network. orfdelayr means, or; to.any. particular way: of taking. the;

seam, i L07 1 L]... E L2. L143;- j L4. 5 I153 l L6 L7 R-e-p'etitio-n--.1. V

Rate; ;2o;oo0.- 19.950. 119.900. 19.850." 49.800." j19l7501-j19.700119mm- 0. e 0;- 1 5& 0: s5? o: 0- 9'. 9; 8t 81 7. 7: 6: o 9.: 1 9:: 9 9:9: I 9; 2-1 H 1. 1;; 11-5. 1: 1.1 u;-

e u' e other suitable :djelay'meansarezwellflinown;in;the

The. delay switches; S21), .SBD; 84D; and: D? are similar to the;switches illustratedior: deter-:- mining the repetition period; and.they' are connected: to; the chain of counterszin: the sameiway; The:voltages; taken ofi. thezdelayz: switches: are? 7.5;

art. .There. may 'be'jmentioned; By; way or. eacample;delaymultivibrators. and phantastron de lay means. p g 1 It.will be.noted that: since: the last" counter stage: supplidn nulsesi the. gatetubez wjis thebinary Ml, the coincidence tube 81 would supply outputpulses of a repetition period of 20,000 as. orless, depending on theselected repetition period, in the absence of some further circuitaction. Double this repetition period is desired, of .course, fordriving the fast-sweep circuit to obtain the adjustable fast trace f-g(Figure The desired repetition period is obtained by, in

effect, blanking out alternate pulses as indicated in Figure 5 so thatonly the 40,000 s. repetition period pulse U appears on the lead I I9and, therefore, on the lead 9A.

This blanking effect is obtained by applying to the grid of gate tube 60by way of a lead a square wave from the last multivibrator M2. This waveis the same as wave C (Figure 5) excep t that it is of the oppositepolarity, being ;taken off the opposite side of M2 from the sidesupplying the wave C. Thus, the grid of tube 60 1 held negative duringthe master period (see Figure 5) whereby the pulse from the binary MI1,. cannot pass through tube 60 during said period.

I The amounta pulse is delayed is not affected by changes in the pulserepetition rate because the amount of delay is less than the shortest 1'repetition period. In the present example, the

maximum delay desired from the point of measurement (mid-point d, Figure5) is less than 19,650 s. which is the shortest repetition period of thewave D. The resetting action is the only thing that would affect thedelay and this does not occur until the counters have operated for morethan the desired period of delay without any loss of count due toresetting.

The delay switch settings obviously do not that case the output pulse onlead HBA would have. a repetition period of 20,000 s. or less as desiredand the amount of the delay would be measured from the time ofoccurrence of any reset pulse, not just from the reset pulse occurringat the mid-point d as in the navigation system application.

THELEF'ILRIGHT Derr'r SWITCHING Cmcm'rs Left drift circuit The leftdrift switching circuit will now be described more in detail withreference to Figure 2 where it is identified as the circuit LDS enclosedby a broken line block. The 100 kc. oscillator l0 supplies a sine wavesignal 400 through a coupling capacitor 40l to the grid of a vacuum tubeVA provided with a grid leak resistor 402.

The negative pulse 403 for actuating the .left

' drift is supplied from the reset pulse generator 49 (Figure 3A) by wayof lead 42A to the switch arm 404 of the left drift switch 406. Theswitch 406 has three positions, the left position L being for left driftaction. The center position is for no drift action, and the rightposition R is for the right drift action which is obtained by means ofother ganged switches in the circuit RDS described hereinafter.

When the left drift switch 406 is in the left position, the negativepulse 403 is applied through acapacitor 401 to the grid of the tube VA..Dur

18 ing a period controlled by the negative pulse 403. the signal 400from oscillator I0 is prevented from passing through the tube VA. Thisis indicated by the graph 408. The length of time; the tube VA cannotpass signal is determined by. the R. C. circuit comprising capacitor401' -(in the case of slow drift) and the grid leak resistor 402. The R.C. circuit 401, 402 acts as a differentiating circuit to differentiatethe negative pulse 403 and thereby obtain from the front edge. of pulse403 the pulse portion of wave 408. The differentiated pulse is muchshorter thanpulse 403, a fact that is not evident from the drawing sincethe graphs 403 and 408 are drawn to different time scales. Slow drift isalwayobtained when the function switches are in either position switchesis shown at 8. tion, it connects a capacitor4l9 in parallel with No. 2or No. 3. V a v t The tube VA is always biased ofi sufficiently topermit passage of only the positive peaksofthe sine wave 400 asindicated by the clipping level shownin graph 408. 7 Thisbiasing is ofthelgrid leak biasing type, the coupling capacitorl 40l receiving acharge periodically from-.grid..,current flow.

The output pulses from tube VA cause periodic damped waves 400 to appearacross aresonant coil 4 in the plate circuit of the tube. -The frequencyof the damped oscillations is the resonant frequency of the coil 4| l.The wavetrains occur at the frequency of oscillator l0.. T

The damped wave trains 409 are passed thifbi gh a clipping tube VB sothat only the most positive peak of each wave train appears in the.output of tube VB. These peaks appear as negative pulses as shown atMS. and are supplied over the lead 4 l I to the input circuit of thedecade counter IS. The circuit comprising the tubes VA and VB connectingthe oscillator [0 to the decade counter l3 may be referred to. as asignal translating circuit.

Fast Left Drift is obtained if the function switch is on position No.1., One, of thefunction If it is on No. '1 posicapacitor 40'! therebyincreasing the time constant of the R. C. circuit.- This lengthens thebiasing off effect of the negative pulse 403 to increase the number ofpulses that are not passed by the tubeVA.

, From the foregoing description, it will beseen that by means of theleft drift circuit the period of theloran timer cycle (the period ofthepulses on lead Bla. (Figure 3A),for example, thatdrive the slow sweepcircuit) may be increased to obtain the left drift effect. The saidperiodis increased by the described; action since for ashort intervalthecounter chain fails to receivepulses for operating the counter. j

The amount that said period is increased is not limited to these values,but in the presentexample there is about a microsecond increase for thefast drift and about a 10' microsecond increase for the slow drift.

Right drift circuit oi the position .of the function switches. tiabi'nQout the switching circuitsfit willlbe. ap-

:19 The 'ght dr i ft action requires a decrease in the f the loran timercycle. In the 1 present this =is*a'-10 -microse cond decrease for the{f'ne'right drift) or to" the B section ofthe counter befdn'which casethere is a'right drift action) Infthe' case: of. slow 'rightdrift actionwhere j 'tl'iereis' "a "10, sxtdecrea-se in the-periodof the timer"cycle, the firststage 'of decade. counter'No.

ere 'isia' 100 ps.. d-e'crease' in .thepe'riod of. the m1rcyclegthetfirst:stagezof decade counter-No. he j'on lystage in"theicounter chain "halving me-tea muses applied totheB sideof'the Icounter tube. Allother counterstages'havethe' '"""resetgpulse.applied"to'the"'norma11y:reset; side or 'wsidior the'counteritubes. I Oneswitching arrangement Iforj applying .the 'f-resetipulses;in'the mannerdescribed'above is 11- Iu'stratedbyway'of example. Referring. to Figure"IBfit will beiseenthat. the leads foricarr'ying reset .piil ses to. thefirst stagesdfdecades No'..2 and No. 3

""got'o the junction points of 33,000 ohmand 2'70 I .ohm'.resistors,.the270 ohm resistor b'eingconnected;to (ground. l 'Ihe, resistancevalues-are not .lc'iiticalf but'theVallue of the. resistor connected o'"ground should below. with respect. to ithe other n; this [particularswitching arrangement so that herelfis'.effectivelya ground'coh'nectionon. the

.sidelno'tL-receivingthe reset pulses. I LTheIreset.pulsefleads' for thefirst stage of ow ?drift= and-*a' 100 microsecond 'decrease for'i4'34uzare1topen'i reg ardless'mfzithezgiositihn-roiilfliefuricti'on:.switches Manama. eTheEamercon-die faspdfift, 5 'Next'consider th' di'ifticircuits 'wherii theidrift Iii the case'ofthe slowdriftthis is accomplished switches 1065 12 I flgiandi ti tgare:inrtheir: right ba s t t t 'ch wt o nt of'on 'driftfOrJRL-pOSltmn.L'There 'ifllOW: noileftid'rift 3 microsecondg instead of to ero, andaction but there i *eitheria fastrigm drift action the case 'o fthe'fast drift by resettingit to a -0r-'a-'slbw-'ri"g-ht --dr-1ftac'tion depelidi g pon the unto'f t'en (i; exto 100-micr0secondsinstead 0 po tion of the-function switches fl lfiend- 426. M toizerm I Iilssume the case of slow:i ightfdi ift where the By 'fefe'r'r'intmpigure- 3 11-, will beseen that function switches are imeithei Nd'2'oi' No. 3 po'sixcpt for the-first; counter Stageofthe counter i nand.thefdriitswitches are he position R *"decad' No's z and thefirstcounter 'stage-of the n he r set p i se' fl I Z -e es'*to th s umes-deade 1 Io."3,*"2'tll stageso'fthe several -"Ofm e 3V1? fi H'QIB to -sirea "'cou'ri'tersr e ceii e reset pulses "in the'same w'ayfas W i htdrift. "The"reSetDli1Se "pit aybe de s c -ibed in the above-mentiqnedWobdward 'traced-from1lead i42; "through*-sWitch fifiand-lconpplication, that is the'positive reset pulses are ductor 43l+tocOnta'ct 'R of'-sWitch 4 3, t l u' h {plied-m5 theAsside of thecounter'tub'esr vWitch4W3 d co ductort'fi'a tdth-tuh'cti on Inthe caseofthe first stages of'counte decad switch '42'6,aandthrough"swit'chmiltand.cver lead EN .f2iand No.3,"according tothe present 'inven- 4 61 6 Side Of tl'ib VI I efl vision"ismade forapplyingdzh'e positive "Itwill'be seenthat' at' the same time the r'esetresei'rpulse fromieadlz either tothe fA'section -'milse} from lead 42"g'oesto the' A -'-si de- *0f the .of, the counter tube (in whichinstance there is v"first f decadbld t 115th maybe traced from-lead?through driftsw'it'ch this right drift switching position with the'func-' 2 is .the'onlystage in'the counter chain'having 3O'fionfiwitchesjfin eithefpo'sition' NOQ' I Y t e 're'st pulses gapplied'to the "?B side of the he'leads-43l and434 areop'6n.

" "counter, tube. All other counter stages have the t e c se offastright'fdr'ift where f B l pulseapplied to the normally. reset side rthefunc'tion switches are on position no. 1 and the .A sfi'deof the'countertube. drift switches "are on" the-positiofiR. Then the Iii the'waselof "fast light 'driftactionwhere reset p se' romlead""4'2' goes-totheB;side. of

"the first stage tube'of decade-N053 toflgive-a fast right drift.

The reset pulseip'ath m y'ibe-traced "conductor 4'37, through I drift:sswit'ch "423, i over "OVerth 1ead434 tothe Bside of decade N0; 3.

deca'de'No. 2 are identified. asflea'dsl3l andf432.

lThe-resetpulse leads Iron the first .staseof. decade I'No. Rareidentified asieads iss and 434.

parentthat thisresult is obtained. ,J'lSpedi-fically; thereset-pulse.fromilead lz goes J Lthroughthe switch:42 l and over thelead 43l to tthe 5A.? side [of tubeiv -l of decadeNo. 2. The. re-

It wi1l*be seen that at the same'time" the reset pulse 'goes to the A'sidefo'f'the tubefVl in'decade No.'-2. This reset pulse'pa'th may betraced from the lead 42, throu h drift sWit'ch l'Z-Z; over conduc? tor439, through furictioirswitch E24,;over conductor I and through lead 43!to"the'"A' side of tube'Vl. An inspectioniof"the-circuit will showthati,for this fast "right'drift position-30f the "switches the leads 432 and433 are open.

. It should be understood 1 that "my izright drift circuit is not.limited. .tdthe particular arrangement illustrated. If other rates Ofdrifts are desired, iorx examplepthe :idlift rswitching may be appliedto tcounteri'stag'es .other""thari "the first stages. fxIt might be'desirable' to apply the slow andxfast .driftl'switchingito'"difiere'ntsta'ges of the "fRefrringnow to the drift sWitchingshow-n inSame'wunter'de'cade- I I I "1':1='.isure:2,..it-is evident that With-theswitches 40s, Also, the drift switching ed notnecessar'ny 42!, 422, and42a in-jthe, left drift position, the applyitheresetpulses t h "B-'sideof a countpositive reset pulses should be applied to the A g fi t-aright "'d fi a counter side of all tub'esiin thecminter chain regardlessi t m maybe F Q' qj i'p s By 5"areanormally apphed-to the B side;i. 9;,so that the 'B side is'the'iicrm'ally resetside for'the "condition of nodrift. In'that case the'reset pulses would be applied to the A side of astage to obtain right drift. The feature 'of 'impor .Itance is that"toobtain right drift the reset pulses 'areapplied 'tothat side ofapcounter stage that is not the normally reset side.

,- g.aset apulse also-goesthrough switch422, over con- --iductor 436':andiover;lead-433 to: the f-A -"side of .z'the tubefifin'ot; shown) -"inthe first'i-stage' of :decade N0. 3. .zlt'iiivillthe:foundi-thattheiileads 432land 7 described.

of this trace.

ment of the time interval between the A- and B pulses from a pair ofground stations will now be Alignment of A and B pulses POSITION No. 1

After a particular pair of ground stations has been selected with thereceiver set on the No. 1 operation position of the function switches,the A and B 'p'ulseswill appear stationary on the two traces Gr-"b andcd. -The ganged drift switches 406, MI, 422 and 423 are operated todrift one of the pulses onto the upper trace cd and over the fixed indexmarker at the left end The other pulse will now appear on the lowertrace 11-12. The pulse on the trace -12 is the A pulse and the pulse onthe trace 11-1) is the B pulse. That thisis true will be evident byreferring to the graphs of Figure 5.

I 'Next, the starting time tof the variable index marker of wave V isadjusted by setting the delay switch knobs ID, 2D, etc. to bring thevariable index-marker under the B pulse. The variable index marker isnow carefully adjusted so that its position with respect to the B pulseis substantially the same as the position of the fixed index marker withrespect to the A pulse.

POSITION NO. 2

"Next, referring to Figure 8, the receiver is H switched by the functionswitches to the fastsweep operation position No. 2 which results in theA and B pulses appearing on the traces hi and f-g, respectively. Asshown in Figure 5, the start of the variable index marker pulse of.;wave V determinesthe start of the second fastsweep portionf-g of waveW, the two starting w practically simultaneously. 1 drift switches 406,AZI, etc. (which now p fOduce a slow drift), the A and B pulses aredrifted to the left ends of the traces where they are on the moreexpanded portion of the fast sweeps. They By operating the are thenclosly aligned as shown in Figure 8 by operating one or more of thevdelay switch knobs POSITION No. 3 The final alignment of theA and Bpulses is done on operation position No. 3 with .the two traces f-g andh--i superimposed as shown in Figure 9. The front edges of the A and Bpulses are now exactly aligned, usually by operating only the switchknob ID. The time reading can now be made from the settings of the delayswitch knobsas shown by the positions of the pointers on the knobs ID,2D, 3D, 4D, and 5D.

I stable oscillator for supplying signal to the high frequency end ofsaid chain of counters for driving said chain of counters, a signaltranslating circuit through which signalfrom said oscillator is suppliedto said chain of counters; a drift control circuit comprising meansconnected to said. translating circuit for blocking the passage ofsignal from said oscillator to said chain of count ers for apredetermined period of; time in response to the application of acertain polarity pulse thereto, and means forapplying at will to .22said last means a pulse of said certain polarity which pulse occurs atthe selected repetition rate whereby the repetition period of saidoutput pulse is increased as a function of said predetermined period oftime.

2. In a receiver for a radio navigation system, in combination, a systemdesigned for producing repetitive pulses that may be produced atselected repetition rates, said system comprising a chain of counters ofthe type that must be driven to produce repetitive output pulses, astable oscillator for supplying signal to the high frequency end of saidchain of counters for driving said chain of counters, a signaltranslating circuit through which signal from said oscillator issupplied to said chain of counters; adrift control circuit comprisingmeans connected to said translating circuit for blocking the passage ofsignal from said oscillator to said chain ofcounters for a predeterminedperiod of time in response to the application of a certain polaritypulse thereto, and means for applying at will to said last means a pulseof said certain polarity which pulse occurs at the selected repetitionrate and at the start of the cycle of counts whereby the repetitionperiod of said output pulse is increased as a function of saidpredetermined period of time. i

3. Incombination, a system designed for producing repetitive pulses thatmay be produced at selected repetition rates, said system comprising achain of counters of the type that must be driven to produce repetitiveoutput pulses, each 1 counter having a count-selecting means, aooincidence tube'or circuit, means applying said selected counts fromthe counters of said chain to said coincidence tube whereby it passes anoutput pulse only in response to the selected counts from each counteroccurring simultaneously,

means for resetting said counters by said output pulse and at thesametime restarting the cycle of operation of the counter chain wherebythe repetition rate of said output pulse is determined by the countselection at each of the counters, a stable oscillator for supplyingsignal to the high frequency end of said chain of counters, a signaltranslating circuit through which signal from said oscillator issupplied to said chain of counters for driving said chain of counters; adrift control circuit comprising means connected to said translatingcircuit forblocking the passage of signal from said oscillator to saidchain of counters for a predetermined period of time in response to theapplication of a certain polarity pulse thereto, and means for applyingat will to said last means a pulse of said certain polarity which pulseoccurs simultaneously with and at the same repetition rate as saidresetting output pulse whereby the repetition period of said outputpulse is increased as a function of said predetermined period of time. i

4. In combination, a system designed for producing repetitive .pulsesthat may be produced counts for each counter occurring simultaneously,means for resettingsaid counters by said output pulse and at the sametime restarting the cycle of operation. of the counter chain whereby thesacs-DQ 5 errepetttion xate iofrsaidloutput pulse is determined bltheucount:-se1ection:- at11each of the-counters,

tableluoscillaor fonsupplying signal to 'theh-igh drequencyiendwfsaidchain ofcounters, :asignal lywith:and at the-same repetition ra-teas saidre- Msetting-output pulsewherehy the-.repeti-tionzperiod =of saidoutput puiseis increased asa functionuof saidepredeterminedpericdottime.

1.5.afI1he invention -according to cla'im 4 wherein 2 means is},provided forchanging the time constant said differentiating circuitwhereby the repetii ion-periodnof saidoutputztpulse' may be increased-either: :aracomparatively t-sm-alh amount or a coma paratively largeamount at will.

6. In combination, a system that ris designed for producing i'puls'es:having select-ed repetition ratesfisaidrsystem comprisin a-chain ofcount- 181's, weach counter having a mount-selecting means;azcoincidence tubeor circuit, said select d-counts fromthe counters-ofsaid chain being applied to :said coincid-ence tube whereby. it passesnizoutput; pulsel onlyin: response to the-selected ucounts Jfrom=-each--counter-occurringsimulta- :Ineus1y,--.-means .for: resetting asaidlcountersby .saidoutput=,pulse and at r the same time restart-;ingitheicycle of operationof the counter-chain hereby .the'repetitionzrate of 1 said output pulse is determined :by the countselection at each of the counters a stable -oscillator connectedoto--supplyz signal-to the -.high frequency end tof said counterchain;a-.-driftcircuit comprising switch- :F-il'lg means through whichresetting output pulses 4 areuapplied to=-one of said counters, -.andmeans --inc1udi-ng-1said-"switching means for selectively-:'applyi-ng-saidilastementionedoutput pulses either e-to-wapoint:insaid one: counter which resets said counter chain tozero or to apoint-"in said one ecounter thatlresets saidcounter chain to-a count--other;'-than zero whereby the repetition-period of -'-l :said-outputypulses :may :be decreased'at will by a :period oftime corresponding tosaid count other zthan zero. I Tin -combination, ai system that isdesigned ;fon=,;producing pulsesnlraving selected repetition sates, saidsystemcomprising a chain of counters, ieach-counter comprising aplurality of stages, .-.each stage having "oneside-that producesavoltage in the positive direction at the time its opjpos'itesideproduces-avoltag in'the negative direction, :each -1 counter haVing-Yacount-selecting means, a I coincidence tube-or circuit said-select- 'edcounts from the counters of said chain being iapplied tosaidooincidence; tube whereby it passes ean output pulse only in I responseto the Y selected countsfromeach counter occurring simultaneous-.-*ly;.-means-;for--resetting said counters by's-aiol output ,vpulse:and at the same time restarting the ecycle-of operation of the counterchain whereby ethe repetitionrate =o fsaid output pulse is detersan inedby the-count selection at each-"of the counters;- ai-stable oscillatorrconnected to supply sig-nal-. toxthe;-high f-r'equencyi'zend offsaidcounter tion at 1 each of the counters,

:24 chain adriitcircui-t c mprisingswitchingmeans through whichresetting output pulses 'are' applied to a stage of one of saidcounters, a nd means including said switching means for selectively ap-5 plying saidlast-mentionedoutput puls-es either to the normallyreset-smear to the other side 'of saidelast menti-onedstage whereby therepeti- -tionperiod of saidvoutput pulses m-ay-b'erdecreased at-will.

'10 8. in combination," a :system that is designed :for producingp-ulseshaving selected repetition wra'tes, .said systemcomprising :ach-aintof-icounvters eacheco-unter: comprising -a plurality of stagesriof the multivibrat-or type, each counter. having alcount-selecting'means, a, -:coincidenceltube or cir- -cuit,--.saidiselected I counts from the :counterswf tsaid ichai-nbeing appliedtosaid coincidence tube whereby it- ,'-passes an -output; pulse only'incresponse atotheselected counts fromeeachicounteroccurringsimultaneously, .means for resetting tsameetime restarting thecycle-of operation-of-the .tcounter chain whereby the-:repetitionrateoft-said "output pulse is idetermined lby the *count seleca stableoscillator connected tosupplysignal tothehigh kfrequency end of saidcounterch-ain; Y adrift-circuitcomprising switching means through whichresetting output pulses are applied to "a stage of one of said gcountersg and means' including' said switching means'for selectivelyapplying saidla'st-mentioned i output pulses either to the norm-allyreset side orto the Other-sideof said=last mentioned stage "whereby therepetition period -o'fsaid output pulses may bedecreased-at will.

-9. In -combination, a system that is designed -for producing pulseshaving-selects repetition ratea-saidsystem comprisingachaintor-counters, .-each- I counter coi'nprisihg a plurality of-stages of 0the multivibr-atorl type, each counter having a '-count-selecting means;a'coi'ncidence tube or cir- -cuit, said selected counts "from thecountersof said chain heing appliedto said coincidence tube whereby itpass-es an output pulse only hire- 5 sponse to the selected counts fromeach counter occurring simuItaneousIyJmeans for resetting .said countersby said output pulse and-at the same time restarting the cycle ofoperation *of the counter chain whereby the repetition rate *of saidoutput p ulsehis determined by *the =count selection at each of thecounters; a stable oscil- -r.lator-connected tosupplysignal to thehigh-ire- -qu'ency end or said cou'nterchain; adrift cir- 01111?comprising-switching means through which 5 resetting output'pulses'are'applied to the first stageof one of'said counters, andmeansinclud- 7 mg said switching means for selectively applying saidlast-mentionedoutp'ut pulses either to the left side or to the rightside of said first stage whereby the repetition period of said outputpulsestm-ay be'decreased at'will by a period of t me equal tothe-repetition period of the pulses appearing at the input circuit ofsaid one counter. 10. In a navigation system receiver for receiving 'twotime-spacedypulses that are transmitted in a predetermined time relationfrom'two "geographically-spaced stationsj'saidvreceiverxincludmg acathode-ray tube havinga screen on which said pulses are to appear andhaving'meansfor producing a cathoderay and "directingt'itiagai'nst 1said een, a' deflecting-circuitforproducing success ive s milar--deflecting"waves, means for deflecting saidcathode 'ray successivelyby said i wave Jana. m a j'f xtime-spacedi-pulses td produce' anindication on said screen during saidrdeflections, means for controllingthe repetition rate of said deflecting waves and for controlling thetime. at which alternate deflecting waves start whereby saidtime-spaced'pulses may be aligned on said screen, said last meanscomprising a counter chain and repetition rate switching means and timerelay switching means associated therewith for, producing successivepulsesof said selected repetition rate with alternate pulses having aselected delay, said successive pulses being applied to said deflectingcircuit to produce traces on the screen during each of said time-spacedpulses whereby said selected delay may be made such as to align said twopulses on said screen; a stable oscillator for supplying signal to thehigh frequency end of said chain of counters, a signal translatingcircuit through which signal from said oscillator is supplied to saidchain of counters, a drift control circuit comprising means associatedwith said signal translating circuit for blocking the passage of signalfrom said oscillator to said chain of counters for a predeterminedperiod of time in response to the application of a certain polaritypulse thereto, and means for applying at will to said last means a pulseof said certain polarity which pulse occurs at the selected repetitionrate whereby the repetition period of said output pulse is increased asa function of said predetermined period of time.

11. In a system for determining the time interval between twotime-spaced pulses which recur at a certain repetition rate, said systemin cluding a cathode-ray tube having a screen on which said pulses areto appear and having means for producing a cathode ray and directing itagainst said screen, a deflecting circuit for producing successivesimilar deflecting waves, means for deflecting said cathode raysuccessively by said deflecting waves and means for causing saidtime-spaced pulses to produce an indication on said screen during saiddeflections, means for controlling the repetition rate of saiddeflecting waves and for controlling the time at which alternatedeflecting waves start whereby said time-spaced pulses may be aligned onsaid screen, said last means comprising a counter chain and repetitionrate switching means and time delay switching means associated therewithfor producing successive output pulses of said selected repetition ratewith alternate pulses having a selected delay, means for resetting saidcounters by the undelayed output pulses and at the same time restartingthe cycle of operation of the counter chain, said successive outputpulses being applied to said deflecting circuit to produce traces on thescreen during each of said time-spaced pulses whereby said selecteddelay may be made such as to align said two pulses on said screen; astable oscillator connected to supply signal to the high frequency endof said counter chain, a drift circuit comprising switching meansthrough which resetting output pulses are applied to one of saidcounters, and means including said switching means for selectivelyapplying said last-mentioned output pulses either to a point in said onecounter which resets said counter chain to zero or to a point in saidone counter that resets said counter chain to a count other than zerowhereby the repetition period of said output pulses may be decreased atwill by a period of time corresponding to said count other than zero.

12. In combination, a chain of counters, each counter comprising aplurality of multivibrators connected-cascade, each multivibrator item-jprising onestage ofv the counter,v eachcounterhavingswitchingmeansconnected toits r'nult vibrators for selecting'fa desiredcount, a'coin' cidence ,tube ori'fcircuit to'which theselected countsfrom'the counters areapplied, said coincidence tube passing asignal onlyin response to all the counts applied thereto occurring simultaneously,-means;for applying the output pulse of said coincidence tubeto 'sa'id multivibrators to reset the counters and start the cycle ofoperation again whereby the repetition rate of said output pulse isdetermined by the switch selection of the counts of the counters in saidchain; each counter having additional switching means connected to itsmultivibrators for selecting a desired count, a coincidence tube orcircuit to which the counts selected by said additional switching meansare applied, said last coincidence tube passing a signal only inresponse to all the counts applied thereto occurring simultaneously,means for applying the output pulse of said last coincidence tube to autilization circuit, said last output pulse having a repetition ratedetermined by the switch selection of the counts applied to the firstcoincidence tube and having a delay with respect to the start of thecycle of operation determined by the switch selection of the countsapplied to the second coincidence tube; a drift circuit comprisingswitching means through which resetting output pulses are applied to thefirst stage of one of said counters, and means including said switchingmeans for selectively applying said last-mentioned output pulses eitherto the left side or the right side of said first stage whereby therepetition period of said output pulses may be decreased at will by aperiod of time equal to the repetition period of the pulses appearing atthe output circuit of said one counter.

'13. In combination, a system designed for producing repetitive pulsesthat may be produced at selected repetition rates, said systemcomprising a chain of counters, each counter having a countselectingmeans, a coincidence tube or circuit, means applying said selectedcounts from the counters of said chain to said coincidence tube wherebyit passes an output pulse only in response to the selected counts fromeach counter occurring simultaneously, means for resetting said countersby said output pulse and at the same time restarting the-cycle ofoperation of the counter chain whereby the repetition rate of saidoutput pulse is determined by the count selection at each of thecounters, a stable oscillator for supplying signal to the high frequencyend of said chain of counters, a signal translating circuit throughwhich signal from said oscillator is supplied to said chain of counters;a first drift I control circuit comprising means associated with saidsignal translating circuit for blocking the passage of signal from saidoscillator to said chain of counters for a predetermined period of timein response to the application of a certain polarity pulse thereto, andmeans for applying at will to said last means a pulse of said certainpolarity which pulse occurs simultaneously with and at'the samerepetition rate as said. resetting output pulse whereby the repetitionperiod of said output pulse is increased as a function of saidpredetermined period of time; a second drift control circuit comprisingswitching means through which resetting output pulses are applied to oneof said counters, and means includ-

